Dual pressure control for refrigeration systems



Sept. 10, 1940. cs. E. SELDON 2,214,236

DUAL PRESSURE CONTROL FOR REFRIGERATION SYSTEMS Filed Dec. 9, 19:57

INVENTOR macaw 10,1940 l 2,214,236

UNITED STATES PATENT OFFICE DUAL PRESSURE CONTROL FOR REFRIG- ERATIONSYSTEMS George E. S'eldon, Detroit, Mich. Application December 9, 1937,Serial No. 178,867 20mm. (01.23642) This inventi r lat t dual pressureexheated condition of the refrigerant in the suction pansion valves" forcontrolling the flow of reline at all times, regardless of the pressuresin frigerant to an evaporator or several evaporators the system. Thepressure of the refrigerant at or each of the several sections of oneevaporator the valve is applied to one side of a diaphragm of acompression type of refrigeration system. or bellows and a pressureexerted in response to 5 i There is-at present a class of valves forcontemperature conditions in the suction line is aptrolling the flow ofrefrigerant to evaporators plied to the o h Side the ph m- A. that isknown as thermostatic expansion valves". spring or weight is connectedto the diaphragm in Thermostatic expansion valves are designed tosuchmanner that a constant forceis exerted in regulate the flowofrefrigerant through refrigopposition to the pressure that isresponsive to 10 eration systems in accordance with temperature the tempu e conditions in the Suction 11116 conditions in predetermined parts ofthe system. of the compressor. This force, therefore, is added Thepredetermined parts of the system usually to the pressure exerted by therefrigerant at the are the expansion valve and the suction line ofvalve. The pressure that is responsive to the h pressor. The valves areso designed that temperature conditions of the suction line, therevthetemperature of the refrigerant in the suction fore, must be higher thanthe pressure of the reline of the compressor must be a predeterminedfrigerant at the valve. To secure ahigher presnumber of degrees higherthan the temperature sure at the suction-line, the suction line must beof the refrigerant at the valve, before the valve hotter than the valve.Since the valve will be will open. Since the refrigerant at the valve isat the boiling point. the suction line will be hot- 20 at 'the boilingpoint, the requirement of 'additer and willvaporize all of therefrigerant passtional degrees of temperature in the suction line ingtherethrough. The operation of the valve. is of the compressorguarantees that the refrigersuch that until the temperature of thesuction ant in the suction line will be superheated and, line is apredetermined number of degrees higher therefore, completelyin the vaporphase. Bethan the temperature of the refrigerant at the 25 cause therefrigerant in the suction line of .the valve, the valve will be closed.When the temcompressor is completely in the vapor phase, it perature ofthe suction line is high enough to is impossible for liquid refrigerantto flow into superheat the refrigerant at the pressure and in thesuction line of the compressor. This avoids the system, the valve opens.The valve is demechanical breakdowns that follow the presence signed tostay open as long as the tempe tu 80 Y of liquid refrigerant in thesuction line of the differential between the bulb and the valve equalscempressorv or exceeds a predetermined value, and is designed Thepressure of the refrigerant in a refrigerato close when the temperaturedifferential fails tion system is constantly changing as the amount toequal the predetermined value.

\ 5 of heat in the liquid tobe cooled changes. To Varioustemperature-responsive media have adequately. protect the refrigerationsystem from been used in the bulb thatis situated in heatthe flow ofliquid refrigerant into the suction conducting relation with the suctionline ofthe line of the compressor, it is necessary that the compressor.ihe media which has been found to refrigerant in the suction line besuperheated. be most satisfactory ls'a'media in both the liq d 4 ns ychanging Pressure in h y m r ture range of the valve, that possesses thetem- Sults in ednstantly, changing bo l p int forperature-pressurecharacteristics of the refri h r r er t a n tantlychangin temrant. Such a media will permit the valve to stay peraturelevel required to insure a superheated open as long as the predeterminedtemperaturecondition of the refrigerant in the suction line ofdifferential exists between the refrigerant at the the p 'e Ittherefore, impractical to valve and the refrigerant in the suction lineof set a fixed temperature level in the suction lineto the compressor.This permits the use of full assure a superheated condition of therefrigerant evaporator capacity under all evaporator condittherein.Adequate protection for the compressor tions. The use of such amediamakes possible ardless of the pr in the y m Th and the vapor phaseduring the normal tempera- 40 can be afforded byv a dual pressureexpansion the use of a limited charge in the b- A 50 valve whichmaintains a temperature level in ited charge is partially in the liquidand partially the suction line of the compressor that is a prein thevapor phase durin he Hormel p -f I determined and constant number ofdegrees ture range of the valve but the mediav is com-,

r above the temperature level of the refrigerant at pletely in the vaporphase when the temperature the valve. Such a valve will maintain asuperinthe suctipn line rises above a predetermined 5 temperature aftera predetermined temperature is reached. This permits the valve to openin response to increases of temperature in the suction line, until thetemperature reaches a predetermined level whereupon the valve will closebecause the media in the vapor phase will be unable to keep pace withthe rising pressure of the refrigerant at the valve. The pressuresexerted by the refrigerant in the suction line at temperatures above thepredetermined level are so much greater than the normal operatingpressure, that the motor which operates the compressor would beoverloaded. Such; overloading can-seriously injure the motor and greatlyshorten its life. The

use of a limited charge inthe 'bulb prevents the opening of the valvewhen the temperature and pressure of the refrigerant in the evaporatorrise above a predetermined level.

Dual pressure expansion valves that are now 1 being used are dividedinto two classes. The first class is known as the insulated fluid type.-This type of valve has a bulb situated in heat-conducting relationwith-a portion of the suction line of the compressor, an expansiblebellows within a valve casing, operating in response to pressuresexerted by the bulb; thattends to open the valve, and an expansiblebellows, responsive to the pressure of the refrigerant in theevaporator, that tends to close the valve. There are twotemperature-responsive bellows within the casing surrounding the valve thatexert a force on the valve, but'the two bellows must be insulated fromeach other. In such valves, definite temperature relationships must bemaintained between the bulb and the two bellows to insure continuedoperation of the valve.

The other type of dual pressure expansion valve is known as the intimatefluid type. In

this type pressure corresponding to the heat of the refrigerant in thesuction line of the compressor is applied to one side ofapressure-responsive diaphragm and tends toopen the valve, while thepressure exe ted by the refrigerant at the valve is exerted on the otherside of the pressure-responsive diaphragm and tends to close the valve.This type of valve has a simpler construction than that used in theinsulated type valve but must still maintain definite temperathe hottestliquid be in the ii'ulb. In the case of the insulated fluid typeexpansion valve, the only liquid, in the part of the control which tendsto open the valve, is situated in the bulb. The pressuremesponsivebellows located in the valve casing must, therefore, be warmer than thebulb to prevent accumulation of liquid in the bellows. The accumulationof liquid in the bellows would serve to shiitthe control of the valvefrom the bulb to the valve casing, and the temperature of the latterwould control. This obviously would be undesirable and, therefore, it isnecessary that the bulb be cooler than the bellows. Such a requirementprevents the immersion of the valve of the valve casing in the liquid tobe cooled and makes it advisable to locate the bellows outside of thecooling compartment. Such a requirement seriously limits theversatilityand utility of this type of valve. In the case of the intimate fluidtype expansion valves. the design is such that the temperature ofthemedia on each side of the pressure-responsive diaphragm isapproximately the same, exclusive of outside influences. Since thetemperature of the refrigerant in the valve is lower than thetemperature in the suction line of the compressor, the bulb is usuallywarmer than the media in contact with the pressure-responsive diaphragm.Since-the media condenses in the cooler portions of the control system,media will be folmd in the liquid phase next to the pressure-responsivediaphragm. In order for the control to be in the bulb where it shouldbe, the liquid inthe bulb must be hotter than the liquid next to thepressure-responsive diaphragm.

- For this reason, the valve casing which containsthepressure-responsive diaphragm cannot be immersed in very hot liquids,because the liquid in the casingwould be hotter than the liquid in thebulb, and the control would shift from the bulb to the valve casing.This condition is disadvantageous and seriously limits the utility ofthis type of valve.

The shifting of controlto which all dual pressure valves now in use aresubject is undesirable and makes ,the-valves ineflective as a regulatorof the flow of refrigerant in accordance with the superheat in therefrigerant in the suction line.

The applicant avoids this condition by absolutely confining the media inahousing in the bulb and transmitting the pressure exerted by the mediato the pressure-responsive diaphragm in the valve casing bysubstantially heat-insensitive means. Such an arrangement permanentlyrestricts the control to the bulb, and insures the proper operation ofthe valve in accordance with the s perheat in the refrigerant in thesuctionvalve does not touch the evaporator, since the capillary tube isfilled with media. Ifthe tube were cooler than the valve or bulb, themedia would condense there and might shift the control from the bulb.Bucli a condition has been knownto exist in practice, and it endangersthe safety of the refrigeration equipment. The applicant avoids such aproblem by transmitting pressures generated in the bulb by asubstantially heatinsensitive liquid.

It is sometimes desirable to use one control for a number ofevaporators. With every other. valve known in the prior art, such anarrangement would necessitate the re-engineering of the bulb and valve.The device of the applicant 'alone can use the same bulb for one or morevalve casings.

It is an object then of this invention ,to provide a refrigerant controlvalve responsive to the superheat of the refrigerant wherein thetemperature of the valve inno wise modifies its action or limits itsadaption to a restricted field.

It is another object to provide a valve adapted '2,214,ase 3 to remainclosed above a fixed evaporator.pressure yet requiring no insulation ofthe power element from the rest of the valve thereby reducing its cost.v 5 It is a further object to produce a valve and a temperatureresponsive bulb independent of each other for purposes of manufacture,shipping and field assembly, but complementary in actual use. a e 1 Itis a further object to provide a thermostatic bulb and closed pressurecontrol system whereby one thermostatic bulb can control more than one.valve... It is a further object to provide a valve or 15 cluster ofvalves controlled by a closed hydraulic system having a hydraulic brakein thesystem to dampenthe fluctuations of the valves. 7

Other objects will be apparent to one versed in the art from thefollowing description and the 20 accompanying drawing. f

The drawing shows a compression type refrig- 'eration system as appliedto a cooling evaporator of two sections one of which is below the otherand in a tank 39 containing water. The numeral I denotes a compressor, 2is a condenser,

3 a reservoir, 4 a liquid refrigerant line to two dual pressureexpansion valves 5 and 6 discharging into two sections] and 8 of theevaporator which is connected to the return mani- 30 fold 9 leadingtothe compressor. Clamp. I0

holds 'the master thermostatic bulb in intimate contact with the returnmanifold allowing the free exchange of heat between them.

The master thermostatic bulb II contains two 35 chambers an inner I2 andan outer I3 separated by a pressure responsive surface which in thiscase is bellows I4. A casing I5 forms the outside wall and has outletfitting I! which is brazed to connecting pipe I8. Orifice I9 forms thecon- 40 nection between this chamber I3 and the tube I8. The innerchamber is charged with the volatile thermostatic fluid through tube I6of the chamber sealing header 2! and is surrounded by the inerthydraulic liquid filling chamber I3.

5 and passing out through the orifice I9 into the closed and sealedhydraulic control system.

The orifice acts as a hydraulic brake checking the tendencies of thehydraulic liquid to respond to fluctuations set up by the needle in thevalve 50 seat. The inner chamber is charged with the volatilethermostatic fluid which is usually the same as the refrigerant used inthe refrigeration system and preferably charged at a pressure lower thanthat corresponding to the charg- .55 ing temperature, therebyestablishing a pressure below which the charge is partly in vapor phaseand partly in liquid phaseeand above which it is entirely in vapor phaseand the pressure no longer increases according'to the characteristic 60vapor pressure temperature relation of the hind but rather the laws ofBoyleand Gay-Lussac.

Hence within the temperature range of the valve the charge can be soadjusted in amount that a definite predetermined pressure is the maximum5 thecharge can exert and consequently the maximum that the hydraulicliquid can .be subjected to and in turn can exert.

The closed hydraulic control system comprises chamber is, tube I8,header 2 tubes 22 and 2a 7 and the hydraulic liquid control chamber ,of

the valves as shown in section at 25. Header 2| distributes thehydraulic control liquid to the valve or valves of the system, it alsoserves as a disconnecting and filling point. The tubes I6. 75 22 and 23are brought to this header and there without disturbing the operationof-the other valve. The number of valves that can be con- .trolled byone master thermostatic bulb is governed by the relative size of thebellows I4 and 10 the area and movement of diaphragm 29. The closedsystemis charged with liquid through opening in the header 2| normallyclosed by plug 24.

Filling the closed hydraulic control system with the liquid is anoperation that can readily be performed in the field though usually the'con-' nections will be -made at the plant making the assemblies. Howeverif necessary say to lengthen the tube connecting the-bulb and the valvein the field such lengthening can be accomplished by simply opening thecontrol system brazing in the required length of tubing and refillingthe system with liquid and replacing plug 24. Heretofore such alengthening of a tube in the field was most inexpedient if notimpossible,

especially with vapor charged valves using the maximum operatingpressure charge. Not only is it now possible to lengthen the tube in thefield but also to add additional valves or thread the connecting tubethrough a hole too small for the bulb in a fitting or evaporator walland connect the bulb on the other side.

Since valves 5 and 6 are of identical construction it will suifice todescribe one only, consider 6. The control liquid enters the dualpressure valve through sweat-connection which isthe means for connectingthe valve to the closed con-- trol system; and the tube 22 is soldersweated or brazed tothe valve at this point. There is also orifice 21which can be a hole of very fine bore say .016 inch diameter. Theorifice is a means for dampening the fluctuations and-vibrationssometimes set upby the throttling action of needle valve on the orificeseat. The hydraulic liquid control chamber 25 of the valve is made ofthe cover 28 and the pressure responsive surfacethe diaphragm 23. On theother side of the diaphragm is the chamber 30 which is ported to connectwith the outlet and tube 3I of the evaporator section 6. Housing 32forms the other side of chamber 30. Orifice 33 opens into this chamberand has needle valve 34 placed therein and adapted to close it andregulate the size of the opening available tothe Iii;v

liquid refrigerant entering the valve through refrigerant line 4; Thevalve 34 can be moved oflits seat by the action of the diaphragm due topressure of'the hydraulic control liquid, theaction of the valve is alsomodified by thespring 0 35 with its adjustment screw 36 and this spring35 is the means-used to apply an 'exteriorload to the pressure sensitivesurface.- Gasket 31 and screw 38 close the valve. In action during therefrigeration cycle, after the motor has started .65 the compressorbegins to draw the refrigerant vapor out'of the evaporator thus loweringthe ,terior spring load the valve opens and allows imately that of theevaporator and the valve can not open due to the fluid and therefrigerant acting on the same effective area of the pressure responsivesurface. The valve can only open when the pressure in chamber 25 isgreater than the combined pressure of chamber ill and the spring load.But the pressures in 25 and 30 would be equal for equal temperatures soit is apparent that the spring 35 is useful to regulate the differenceof temperature between the two points considered, in'other words theload of the spring -35 controls the superheat of the vapor. It will alsobe seen that each dual pressure valve in the refrigeration system canhave its own superheat setting without interference fromthe other valvesof the system and each valve can be adjusted to compensate forvariations of load and refrigerant head on it. It is also feasible tohave several evaporator-s at different points similarly controlled, i.e. a valve on each evaporator and a master bulb at the outlet of one' ofthem. .It will beseen for such operation the bulb containing thevolatile fluid is in intimate contact with an outlet pipe leading fromthe evaporator which pipe with its rapidly moving refrigerant is a bodyhaving more than ample thermal capacity to control the temperature ofthe bulb and consequently its vaporization pressure. This vaporizationpressure is converted at the bulb to hydraulic pressure at practicallythe same value which in turn can control the refrigerant flow to severalevaporators through dual pressure valves. These evaporators need not bein the same refrigeration system, it is only necessary that the othersystem operate at a temperature so related to the master system in whichthe bulbJs' located that the temperature difference comes within therange of the spring adjustment available, and the refrigerant usedshould be the same or have substantially similar characteristics and theevaporators should have approximately the .same elevation.

What I claim and desire to secure by Letters Patent 'of the UnitedStates is: y

1. A dual pressure control for a refrigeration system comprising a valvecasing having an inlet for refrigerant, an outlet for refrigerant, a

valve adapted to regulate the flow of refrigerant through said valvecasing, a pressure-responsive diaphragm to operate the valve, meansbiasing the valve to closed position, means to permit refrigerant atevaporator pressure to contact one" side of the diaphragm and exertpressure thereon tending to close the valve; a'feeler bulbcasing havingan expansible bellows positioned therein and attached thereto, saidfeeler bulb casing containing a temperature-responsive media thatpartially in the liquid and partially in the vapor phase throughout thenormal temperature range of the feeler bulb casing and completely in thevapor phase whenever the temperature of the feeler bulb casing risesabove a predetermined level, said temperature-responsive media beingadapted to exert pressure on the expansible bellows in response to thetemperature in a predetermined portion of the refrigeration system,

- and a hydraulic system comprising a fluid tight chamber in the valvecasing having a portion of one of its walls formed by thepressure-responsive surface, .tubing connecting'said fluid tight chamberand the feeler bulb casing, and a substantially heat-insensitive liquidcompletely filling the fluid tight chamber in the valve casing thetubing connecting theifluid tight chamber and the feeler bulb casing andthat part of the feeler bulb casing not occupied bytemperatureresponsive media, said hydraulic system being adapted totransmit pressure from the bellows,

, phragm, an inlet for refrigerant, an outlet for refrigerant, a valveadapted to regulate the flow of refrigerant through said valve casingsaid pressure-responsive diaphragm being adapted to operate the valve,means biasing the valve to closed position, means to permit refrigerantat evaporator pressure to enter the refrigerant chamber and contact thepressure-responsive diaphragm and eiert pressure thereon tending toclose the valve; a feelerbulb casing having an expansible bellowspositioned therein and attached to one end thereof, said feeler bulbcasing containing a temperature-responsive media that is adapted toexert pressure on the expansible bellows in response to the temperaturein a predetermined portion of the refrigeration system, saidtemperature-responsive media being partially in the liquid and partialyin the vapor phase throughout the normal temperature range of thefeeler'bulb casing and completely in the vapor phase whenever thetemperature of the feeler bulb casing rises above a predetermined levelwhereby the pressures exerted by said temperature-responsive mediaincrease greatly for small increases in temperature during the 'normaltemperature range of thefeeler bulb casing and increase slightly forlarge increases in temperature whenever the temperature of the feelerbulb casing rises above a predetermined level,

ing'said hydraulic chamber, the tubing connecting 'the feeler bulbcasing with the hydraulic chamber and that part of th feeler bulb casingnot occupied by temperature-responsive media,-

said lwdraulic system being adapted totransmit pressure from the bellowsin the feeler bulb casing to the other side of the pressure-responsivediaphragm in the valve casing whereby the temperature conditions at thevalve casing cannot directly affect the temperature responsive media,said pressure transmitted by the hydraulic system being adapted to biasthe valve to open position. 1

GEORGE E. SELDON.

